In rotating shaft machinery, it is necessary to lubricate the shaft supporting bearings, or journals as they are often referred to. The bearings function as the main support for the rotating shaft whether the latter be driven, or be part of a driving mechanism such as a motor or an engine.
It is normal practice in any embodiment or form of bearing, whether it be roller, sleeve or otherwise, to assure that the bearing is provided with sufficient lubricant to establish a friction resistant layer between adjacent surfaces of rubbing parts. Proper bearing lubrication will normally assure extended, efficient operation of the equipment and minimize bearing burn out. The latter could be the consequence of any failure in the lubrication system.
Lubricants can assume different forms depending on the application to which they are applied. In most instances, the lubricant will conveniently take the form of a liquid having particular characteristics. The liquid is directed into or onto the bearing in a manner to maintain the necessary interface film.
Where a liquid lubricant is utilized, the operating conditions, particularly the rotational speed of the machine or equipment, may be such that the load applied to the shaft could generate excessive heat. When the heat is sufficient to break down the lubricant, or where the lubricant does not reach the necessary bearing surfaces, the latter will soon deteriorate and hasten prompt bearing wear.
It is essential therefore that not only should lubricant flow be maintained onto a journal or bearing surface, but the lubricant must be kept within a preferred temperature range that will assure its effectiveness.
Diverse ways and methods have been utilized toward achieving effective lubricant cooling primarily by the facility of heat transfer with another medium such as oil, water, air or the like. In either instance, the lubricant is generally maintained in a reservoir communicated with, or within the bearing housing.
Heated lubricating oil which passes into the reservoir is circulated through or in contact with a heat exchange means which can be located close by, or which can be remote from the equipment. Thereafter the cooled lubricant is recirculated for reintroduction against the bearing surfaces.
In one embodiment, particularly where several bearings are involved, the lubricant holding reservoir can be maintained in a casing or housing which encloses the bearing. Further, lubricant can be delivered to the bearing surfaces in a pressurized stream by a pump rather than by way of a splash system.
It can be appreciated that rotating machinery of the type here contemplated, which is physically locationed in an area that experiences a shortage of water, can realize a negative operating factor in the bearing cooling process. This is notably true in arid and desert areas where water is in short supply, or immediately inaccessible.